Duplicating items

As shown on this video by another person, (https://www.youtube.com/watch?v=KCsUdcs9JDw), Your able to duplicate stuffs, i decided to go into my world, i went in and test it out, i built several of them and tested it, it is hard to do it but your able to duplicate the thing when you take the object out of the chest right when it's being pushed away by the piston.